PDF Merge

What this tool is used for

• Combining scanned pages that arrived as separate files into a single document to send.
• Assembling an appendix onto the end of a report before sharing it.
• Putting a cover sheet in front of an existing PDF.
• Merging chapters exported separately so page numbering can be checked as a whole.
• Combining receipts or invoices into one attachment for a claim.

Frequently Asked Questions

What happens to bookmarks and links when merging?

Internal links and outlines often break, because page destinations are absolute references that shift when documents are concatenated. Good mergers remap them; many simply drop the outline, which is why merged PDFs frequently lose navigation.

Are form fields preserved?

Only with care. AcroForm fields live in a document-level catalogue and field NAMES must be unique — merging two copies of the same form produces colliding names, so values entered in one appear in the other.

Does merging re-compress the pages?

No. Page content streams are copied verbatim, so there is no quality loss and the output is roughly the sum of the inputs. Size reduction requires a separate optimisation pass.

What if the pages are different sizes?

They stay different — PDF stores a MediaBox per page, so an A4 and a Letter page coexist happily in one file. That is correct behaviour, though it can look wrong when printing without scaling.

Can I merge an encrypted PDF?

Not without the password. A permissions-only PDF (owner password, no user password) may open but still forbids modification, and honouring that restriction is the correct behaviour rather than a limitation.

What happens to conflicting document metadata?

The first document's usually wins, so the merged file inherits its title, author and creation date. That is rarely what you want for a compiled document, and it is worth setting explicitly afterwards.

Do embedded fonts get deduplicated?

Only if the merger subsets and compares them, and many do not. Merging ten documents using the same font can embed it ten times, which is why a merged file is often larger than the sum of its parts.

Common errors and gotchas

• Merging without checking the order, since the order files were selected in is not always the order they appear.
• Assuming form fields survive. Merging often flattens or collides field names across documents.
• Losing bookmarks and internal links, which frequently do not carry across a merge.
• Overlooking mixed page sizes, which produces a document that prints inconsistently.
• Expecting a merge to reduce size. It is roughly additive, and duplicated fonts may not be shared.